The copolymers of olefins and SO.sub.2 are well known in the art. These polymers may be prepared by various processes, including bulk, solution and emulsion polymerization. These polymers have various uses, including as thickeners for crude oil, coatings, viscosity index improvers, etc.
U.S. Pat. No. 2,652,368 teaches the use of copolymers of SO.sub.2 and olefins in lubricating oil compositions. These copolymers are prepared by the polymerization of a monomeric olefin and sulfur dioxide.
U.S. Pat. No. 3,442,790 teaches olefin sulfur dioxide copolymers as wax crystal modifiers. These materials are essentially alternating copolymers of a monomeric olefin and sulfur dioxide. The patentees note that there may be some homopolymerization of olefin taking place. This reference, however, does not teach the block copolymers of the instant invention.
U.S. Pat. No. 2,853,373 teaches the use of a copolymer of SO.sub.2 and a C.sub.8 to C.sub.24 olefin. These materials are prepared by the copolymerization of the monomeric olefin and sulfur dioxide in a manner known in the art. Thus, this reference does not teach the block copolymer of the instant invention.
Dainton et al., J. Polymer Sci., 26, pages 351-64 (1957); 29, pages 549-56 (1958) teach polymers formed from the monomeric olefin and SO.sub.2. These materials, since they are prepared by monomeric olefins, are unlike the block copolymers of the instant invention.
In U.S. Pat. Nos. 3,409,548; 3,396,115; and British Pat. No. 1,258,758 copolymers of olefins and sulfur dioxide are taught as useful in oil-based fracturing fluids; dry cleaning solvents; and coatings, respectively. All these materials are prepared by the copolymerization of sulfur dioxide and a monomeric alpha-olefin. Thus, they are unlike the compositions of the instant invention.
U.S. Pat. No. 3,563,961 teaches a process for the preparation of terpolymers of alpha-olefin, sulfur dioxide and monoolefinically unsaturated carboxylic acid chlorides or monoolefinically unsaturated dicarboxylic anhydrides. These polymers are not characterized as block copolymers, since they are prepared from mixtures of the respective monomers.
Crawford et al., J. Appl. Poly Sci., 15, pages 1881-1888 (1971) teach copolymers of alpha-olefins and sulfur dioxide. In the preparation utilized in this paper, the olefin was added slowly to liquefied sulfur dioxide. Thus, the resulting copolymer was not the block copolymers of the instant invention.
In U.S. Pat. 3,728,185, the use of olefin sulfur dioxide copolymers as bonding agents for finely divided inorganic fusible or sinterable material is disclosed. The olefin-sulfur dioxide copolymer is prepared by methods known in the art, that is, the copolymerization of monomeric olefins and sulfur dioxide in the presence of free radical catalysts or ultraviolet light. These materials, since they are prepared from mixtures, including monomeric olefins, do not have the block copolymer structure of the compositions of the instant invention. In German Application 2,308,415 and netherlands Application 73,02322, copolymers of two monoolefins and sulfur dioxide are taught. These materials are prepared from mixtures of the monomeric olefin, thus block copolymers similar to those of the instant invention are not taught.
U.S. Pat. 3,313,785 claims block copolymers of olefin-SO.sub.2 and a free radical polymerizable monomer, e.g., vinyl chloride, ethyl acrylate, etc. are prepared by adding said monomer to a "living" polymer prepared by the auto initiated copolymerization of the olefin and SO.sub.2. The teachings of this reference have been refuted by G. Sartori et al. in Polymer Letters, Vol. 10, pages 583-592 (1972). The disclosure of this patent differs from the instant process in that it does not teach the generation of free radical containing segments by use of shear, which are utilized in initiating the polymerization of an added monomer. Furthermore, since the patentee teaches a free radical polymerization mechanism, there is no disclosure of how to make block copolymers containing monomers which do not undergo free radical polymerization, e.g., isobutene, ethylene oxide, etc.
The novel block copolymers of the instant invention may be used in all of the applications described for olefin-SO.sub.2 polymers above. However, as will be apparent to the skilled artisan the properties of the novel copolymers described below may provide more or less effective use in said applications.